diff --git a/app/models/issue.rb b/app/models/issue.rb
index 2d9228b..8a0ef7f 100644
--- a/app/models/issue.rb
+++ b/app/models/issue.rb
@@ -68,6 +68,8 @@ class Issue < ActiveRecord::Base
   validates_length_of :subject, :maximum => 255
   validates_inclusion_of :done_ratio, :in => 0..100
   validates_numericality_of :estimated_hours, :allow_nil => true
+  validates :start_date, :date => true
+  validates :due_date, :date => true
   validate :validate_issue, :validate_required_fields
 
   scope :visible, lambda {|*args|
@@ -532,14 +534,6 @@ class Issue < ActiveRecord::Base
   end
 
   def validate_issue
-    if due_date.nil? && @attributes['due_date'].present?
-      errors.add :due_date, :not_a_date
-    end
-
-    if start_date.nil? && @attributes['start_date'].present?
-      errors.add :start_date, :not_a_date
-    end
-
     if due_date && start_date && due_date < start_date
       errors.add :due_date, :greater_than_start_date
     end
diff --git a/app/models/version.rb b/app/models/version.rb
index 50225f3..e7651ad 100644
--- a/app/models/version.rb
+++ b/app/models/version.rb
@@ -30,10 +30,9 @@ class Version < ActiveRecord::Base
   validates_presence_of :name
   validates_uniqueness_of :name, :scope => [:project_id]
   validates_length_of :name, :maximum => 60
-  validates_format_of :effective_date, :with => /\A\d{4}-\d{2}-\d{2}\z/, :message => :not_a_date, :allow_nil => true
+  validates :effective_date, :date => true
   validates_inclusion_of :status, :in => VERSION_STATUSES
   validates_inclusion_of :sharing, :in => VERSION_SHARINGS
-  validate :validate_version
 
   scope :named, lambda {|arg| where("LOWER(#{table_name}.name) = LOWER(?)", arg.to_s.strip)}
   scope :open, lambda { where(:status => 'open') }
@@ -287,10 +286,4 @@ class Version < ActiveRecord::Base
       progress
     end
   end
-
-  def validate_version
-    if effective_date.nil? && @attributes['effective_date'].present?
-      errors.add :effective_date, :not_a_date
-    end
-  end
 end
diff --git a/lib/redmine/core_ext/active_record.rb b/lib/redmine/core_ext/active_record.rb
index b18f95c..69bf76a 100644
--- a/lib/redmine/core_ext/active_record.rb
+++ b/lib/redmine/core_ext/active_record.rb
@@ -38,3 +38,14 @@ module ActiveRecord
     end
   end
 end
+
+class DateValidator < ActiveModel::EachValidator
+  def validate_each(record, attribute, value)
+    before_type_cast = record.attributes_before_type_cast[attribute.to_s]
+    if before_type_cast.is_a?(String) && before_type_cast.present?
+      unless before_type_cast =~ /\A\d{4}-\d{2}-\d{2}\z/ && value
+        record.errors.add attribute, :not_a_date
+      end
+    end
+  end
+end
diff --git a/test/unit/version_test.rb b/test/unit/version_test.rb
index ecc0d22..fa695fe 100644
--- a/test/unit/version_test.rb
+++ b/test/unit/version_test.rb
@@ -37,6 +37,8 @@ class VersionTest < ActiveSupport::TestCase
     assert !v.valid?
     v.effective_date = '2012-31-11'
     assert !v.valid?
+    v.effective_date = '-2012-31-11'
+    assert !v.valid?
     v.effective_date = 'ABC'
     assert !v.valid?
     assert_include I18n.translate('activerecord.errors.messages.not_a_date'),